Structure status determination device, status determination system, and status determination method

ABSTRACT

The purpose of the present invention is to accurately detect, from a remote location without contact, a structure&#39;s defects such as cracking, separation, and internal cavities by distinguishing therebetween. The status determination device includes: a displacement calculation unit that, from time-series images of a structure surface before and after loading application, calculates a two-dimensional spatial distribution of a displacement of the time-series images; a depth moving amount calculation unit that calculates a moving amount of the structure surface in a normal direction due to the loading application, from the two-dimensional spatial distribution of the displacement of the time-series images; a displacement separation unit that calculates a correction amount based on the moving amount, and separates a two-dimensional spatial distribution of a displacement of the structure surface, by subtracting the correction amount from the two-dimensional spatial distribution of the displacement of the time-series images; and an abnormality determination unit that identifies a defect of the structure, based on comparison of the two-dimensional spatial distribution of the displacement of the structure surface and the moving amount, with a spatial distribution of a displacement having been prepared in advance and a threshold value for the moving amount.

This application is a National Stage Entry of PCT/JP2016/001428 filed onMar. 14, 2016, which claims priority from Japanese Patent Application2015-057048 filed on Mar. 20, 2015, the contents of all of which areincorporated herein by reference, in their entirety.

TECHNICAL FIELD

The present invention relates to a technique to remotely determine thestatus of defects or the like caused in a structure.

BACKGROUND ART

Defects (cracks, separations, or internal cavities) caused on thesurface of a concrete structure such as tunnels and bridges are known toaffect the soundness of the structure. It is thus necessary toaccurately detect these defects so as to accurately judge the soundnessof a structure.

Detection of defects of a structure such as cracks, separations, orinternal cavities has been performed by an inspector's visual check orhammering tests, in which the inspector has to approach the structurefor inspection. Therefore, increase in operation costs for preparing anenvironment to facilitate the aerial operation and economic opportunityloss due to traffic control required for setting the operationalenvironment have presented a problem. In view of this, a method toenable an inspector to inspect a structure remotely is desired.

There is a method performed by image measurement has been proposed as amethod to determine a structure status remotely. For example, atechnique has been proposed to subject an image of a structure capturedby an image-capturing device, to binarization processing with apredetermined threshold value, and detect a portion of the binarizedimage corresponding to a crack (PTL 1). There has been also proposed atechnique to detect a cleavage caused in a structure, from the stressstate of the structure (PTL 2, PTL 3). There have also been proposed asystem that determines a failure of an object to be measured byautomatically analyzing the captured image by using both of an infraredimage-capturing device or a visible-light image-capturing device, and alaser image-capturing device (PTL 4), and a method to create a defectmap from the image captured by image-capturing means that is excellentin portability (PTL 5). Furthermore, in NPL 1, a method to enhance theaccuracy in detecting a crack by detecting the motion of the crackedarea, in the moving image of the surface of a structure.

CITATION LIST Patent Literature

-   [PTL 1] Japanese Patent Application Publication No. 2003-035528-   [PTL 2] Japanese Patent Application Publication No. 2008-232998-   [PTL 3] Japanese Patent Application Publication No. 2006-343160-   [PTL 4] Japanese Patent Application Publication No. 2004-347585-   [PTL 5] Japanese Patent Application Publication No. 2002-236100-   [PTL 6] Japanese Patent Application Publication No. 2012-132786

Non Patent Literature

-   [NPL 1] Z. Wang, et al., “Crack-opening displacement estimation    method based on sequence of motion vector field images for civil    infrastructure deterioration inspection”, Image Media Processing    Symposium (PCSJ/IMPS2014), 1-1-17, The Institute of Electronics,    Information and Communication Engineers, Nov. 12, 2014

SUMMARY OF INVENTION Technical Problem

However, with the above-mentioned techniques, for example when capturingan image of the lower surface of a structure such as a bridge, adisplacement (referred to as “out-of-plane displacement”) caused bymovement of the location of the surface to be image-captured in thenormal direction of the surface, due to deflection of the structure bymeans of loading will be added to a displacement (referred to as“in-plane displacement”) of the surface in the in-plane direction havinginformation of the defect of the structure. Accordingly, there is aproblem of accuracy degradation in detection of a defect in a structure.

PTL 6 proposes, in measuring the strain caused on a surface of an objectto be measured, a method to correct the out-of-plane displacement amountbased on the displacement of a captured image. In PTL 6, theout-of-plane displacement amount is read from the side images before andafter the deformation of the structure. For performing this, two videodevices are provided, namely, a first video device that captures animage of the surface of the structure and a second video device thatcaptures the side of the structure.

However, with this method, an extra video device to capture an image ofthe side becomes necessary other than a video device that captures animage of the surface, which increases costs. Furthermore, in case ofbridges or the like, it becomes necessary to fix the image-capturingdevice and to assure the footing of the operators, so as to measure theside of the bridges or the like, which involves unfavorable operabilityand reduces the accuracy in measurement.

The present invention has been made in view of the above problems, andhas an objective to detect with favorable accuracy any defect of astructure, such as cracks, separations, or internal cavities, remotelywithout contact, while restraining costs.

Solution to Problem

A status determination device according to the present inventioncomprises: a displacement calculation unit that, from time-series imagesof a structure surface before and after loading application, calculatesa two-dimensional spatial distribution of a displacement of thetime-series images; a depth moving amount calculation unit thatcalculates a moving amount of the structure surface in a normaldirection due to the loading application, from the two-dimensionalspatial distribution of the displacement of the time-series images; adisplacement separation unit that calculates a correction amount basedon the moving amount, and separates a two-dimensional spatialdistribution of a displacement of the structure surface, by subtractingthe correction amount from the two-dimensional spatial distribution ofthe displacement of the time-series images; and an abnormalitydetermination unit that identifies a defect of the structure, based oncomparison of the two-dimensional spatial distribution of thedisplacement of the structure surface and the moving amount, with aspatial distribution of a displacement having been prepared in advanceand a threshold value for the moving amount.

A status determination system according to the present inventioncomprises: a status determination device that includes: a displacementcalculation unit that, from time-series images of a structure surfacebefore and after loading application, calculates a two-dimensionalspatial distribution of a displacement of the time-series images; adepth moving amount calculation unit that calculates a moving amount ofthe structure surface in a normal direction due to the loadingapplication, from the two-dimensional spatial distribution of thedisplacement of the time-series images; a displacement separation unitthat calculates a correction amount based on the moving amount, andseparates a two-dimensional spatial distribution of a displacement ofthe structure surface, by subtracting the correction amount from thetwo-dimensional spatial distribution of the displacement of thetime-series images; and an abnormality determination unit thatidentifies a defect of the structure, based on comparison of thetwo-dimensional spatial distribution of the displacement of thestructure surface and the moving amount, with a spatial distribution ofa displacement having been prepared in advance and a threshold value forthe moving amount; and an image-capturing unit that captures thetime-series images and provides the status determination device with thetime-series images.

A status determination method according to the present inventioncomprises: calculating, from time-series images of a structure surfacebefore and after loading application, a two-dimensional spatialdistribution of a displacement of the time-series images; calculating amoving amount of the structure surface in a normal direction due to theloading application, from the two-dimensional spatial distribution ofthe displacement of the time-series images; calculating a correctionamount based on the moving amount; separating a two-dimensional spatialdistribution of a displacement of the structure surface, by subtractingthe correction amount from the two-dimensional spatial distribution ofthe displacement of the time-series images; and identifying a defect ofthe structure, based on comparison of the two-dimensional spatialdistribution of the displacement of the structure surface and the movingamount, with a spatial distribution of a displacement having beenprepared in advance and a threshold value for the moving amount.

Advantageous Effects of Invention

The present invention enables detection with favorable accuracy anydefect of a structure, such as cracks, separations, or internalcavities, remotely without contact, while restraining costs.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a statusdetermination device according to an example embodiment of the presentinvention.

FIG. 2 is a block diagram illustrating a specific configuration of astatus determination device according to an example embodiment of thepresent invention.

FIG. 3 is a block diagram illustrating a configuration of a statusdetermination system according to an example embodiment of the presentinvention.

FIG. 4A is a diagram for explaining a relation between the structurestatus (sound case) and the displacement of the surface.

FIG. 4B is a diagram for explaining a relation between the structurestatus (crack case) and the displacement of the surface.

FIG. 4C is a diagram for explaining a relation between the structurestatus (separation case) and the displacement of the surface.

FIG. 4D is a diagram for explaining a relation between the structurestatus (internal cavity case) and the displacement of the surface.

FIG. 5 is a diagram for explaining an out-of-plane displacement at thetime of image-capturing a lower surface of the structure, when thestructure is deflected attributed to loading.

FIG. 6 is a diagram for explaining the relationship between anout-of-plane displacement vector, an in-plane displacement vector, and ameasurement vector.

FIG. 7A is a diagram illustrating a graph of a magnitude of theout-of-plane displacement vector.

FIG. 7B is a diagram illustrating a graph of a magnitude of theout-of-plane displacement vector.

FIG. 8 is a diagram illustrating a magnitude of the out-of-planedisplacement vector and a graph of a magnitude of the out-of-planedisplacement vector.

FIG. 9A is a diagram illustrating a result of calculating, in adisplacement calculation unit, a displacement of a structure surface inX-direction after loading compared to before loading (crack case).

FIG. 9B is a diagram illustrating a result of calculating, in thedisplacement calculation unit, a displacement of the structure surfacein Y-direction after loading compared to before loading (crack case).

FIG. 10A is a diagram illustrating a result of calculating, in adisplacement correction unit, an in-plane displacement of the structuresurface in X-direction after loading compared to before loading (crackcase).

FIG. 10B is a diagram illustrating a result of calculating, in thedisplacement correction unit, an in-plane displacement of the structuresurface in Y-direction after loading compared to before loading (crackcase).

FIG. 11 is a diagram for explaining a calculation method of a correctionamount when there is a tilt, in a correction amount calculation unitaccording to an example embodiment of the present invention.

FIG. 12A is a diagram illustrating a distribution of the stress fieldaround a crack.

FIG. 12B is a diagram illustrating a distribution of the stress fieldaround a crack.

FIG. 13A is a diagram illustrating an example of a two-dimensionaldistribution (X-direction) of a displacement amount around a crack (whenthe crack is shallow).

FIG. 13B is a diagram illustrating an example of a two-dimensionaldistribution (Y-direction) of a displacement amount around a crack (whenthe crack is shallow).

FIG. 13C is a diagram illustrating an example of a two-dimensionaldistribution (X-direction) of a displacement amount around a crack (whenthe crack is deep).

FIG. 13D is a diagram illustrating an example of a two-dimensionaldistribution (Y-direction) of a displacement amount around a crack (whenthe crack is deep).

FIG. 14A is a diagram for explaining a pattern matching with adisplacement distribution (a pattern in X-direction of the displacement)by an abnormality determination unit.

FIG. 14B is a diagram for explaining a pattern matching with adisplacement distribution (a pattern in Y-direction of the displacement)by the abnormality determination unit.

FIG. 14C is a diagram for explaining a pattern matching with adisplacement distribution (a pattern of a differential vector field of adisplacement) by the abnormality determination unit.

FIG. 15A is a perspective view illustrating a two-dimensionaldistribution of a stress on a surface viewed along the image-capturingdirection when there is an internal cavity.

FIG. 15B is a plan view illustrating a two-dimensional distribution of astress on a surface viewed along the image-capturing direction whenthere is an internal cavity.

FIG. 16A is a diagram illustrating a contour (X-component) of adisplacement of a surface viewed along the image-capturing directionwhen there is an internal cavity.

FIG. 16B is a diagram illustrating a contour (Y-component) of adisplacement of a surface viewed along the image-capturing directionwhen there is an internal cavity.

FIG. 16C is a diagram illustrating a stress field on a surface viewedalong the image-capturing direction when there is an internal cavity.

FIG. 17A is a diagram for explaining a response when an impulsestimulation is provided on a structure when there is an internal cavity(illustrating a location ABC at which a response is obtained).

FIG. 17B is a diagram for explaining a response when an impulsestimulation is provided on a structure when there is an internal cavity(illustrating a location ABC at which a response is obtained).

FIG. 18A is a diagram illustrating a contour (X-component) of adisplacement of a surface viewed along the image-capturing directionwhen there is a separation.

FIG. 18B is a diagram illustrating a contour (Y-component) of adisplacement of a surface viewed along the image-capturing directionwhen there is a separation.

FIG. 18C is a diagram illustrating a stress field on a surface viewedalong the image-capturing direction when there is a separation.

FIG. 19 is a diagram for explaining a time response of a displacementwhen an impulse stimulation is provided on a structure when there is aseparation.

FIG. 20A is a diagram illustrating where a structure (sound case) isdeflected due to loading.

FIG. 20B is a diagram illustrating where a structure (deteriorated case)is deflected due to loading.

FIG. 21A is a diagram illustrating an example in which animage-capturing range of a lower surface of a structure is divided intoa plurality of areas.

FIG. 21B is a diagram illustrating an example in which an amount ofdeflection is obtained for each divided area.

FIG. 22 is a diagram illustrating a change of a moving amount (amount ofdeflection) from a start to an end of the loading application.

FIG. 23 is a diagram illustrating a distribution of a characteristicdeflection when there is a cavity inside a structure.

FIG. 24 is a flowchart illustrating a status determination method usedin a status determination device according to an example embodiment ofthe present invention.

DESCRIPTION OF EMBODIMENTS

The following describes example embodiments of the present inventionwith reference to the drawings. Although the example embodimentsdescribed below provide technologically desirable limitations forpracticing the present invention, the scope of the invention is notlimited to the following limitations.

FIG. 1 is a block diagram illustrating a configuration of a statusdetermination device according to an example embodiment of the presentinvention. The status determination device 100 according to the presentexample embodiment includes a displacement calculation unit 101 thatcalculates a two-dimensional spatial distribution of a displacement intime-series images taken before and after loading is applied on asurface of a structure, from the time-series images. In addition, thestatus determination device 100 according to the present exampleembodiment includes a depth moving amount calculation unit 102 thatcalculates a moving amount of the structure surface in the normaldirection caused due to the loading application, from thetwo-dimensional spatial distribution of the time-series images. Inaddition, the status determination device 100 according to the presentexample embodiment includes a displacement separation unit 103 thatcalculates a correction amount based on the moving amount, and separatesa two-dimensional spatial distribution of a displacement of thestructure surface by subtracting the correction amount from thetwo-dimensional spatial distribution of the displacement of thetime-series images. In addition, the status determination device 100according to the present example embodiment includes an abnormalitydetermination unit 104 that identifies defects in the structure based ona comparison among the two-dimensional spatial distribution of adisplacement of the structure surface and the moving amount, and aspatial distribution of a displacement prepared in advance and athreshold value for the moving amount. Note that the direction of thearrows in FIG. 1 is an example, and is not intended to limit thedirection of the signals between the blocks.

FIG. 2 is a block diagram illustrating a specific configuration of astatus determination device according to an example embodiment of thepresent invention. The status determination device 1 includes adisplacement calculation unit 2, a depth moving amount calculation unit3, a displacement separation unit 4, a differential displacementcalculation unit 5, an abnormality determination unit 6, and anabnormality map creation unit 9. The abnormality determination unit 6includes a three-dimensional spatial distribution information analysisunit 7 and a temporal change information analysis unit 8. Note that thedirection of the arrows in FIG. 2 is an example, and is not intended tolimit the direction of the signals between the blocks.

FIG. 3 is a block diagram illustrating a configuration of a statusdetermination system according to an example embodiment of the presentinvention. The status determination system 10 includes a statusdetermination device 1 and an image-capturing unit 11. The statusdetermination device 1 is a device illustrated in FIG. 2. Theimage-capturing unit 11 is an image-capturing camera. Theimage-capturing unit 11 captures an image of a surface of a structure 12before and after loading is applied on the structure 12, as thetime-series images on the X-Y plane, and inputs the captured time-seriesimages to the displacement calculation unit 2 of the statusdetermination device 1. The status determination device 1 obtainstime-series image information from the image-capturing unit 11. In FIG.3, the structure 12, which is an object to be measured, is assumed to bea beam-like structure supported at two points. The structure 12 may havevarious types of defects 13. Note that the direction of the arrows inFIG. 3 is an example, and is not intended to limit the direction of thesignals between the blocks.

The displacement calculation unit 2 of the status determination device 1calculates a displacement for each (X, Y) coordinate on the X-Y plane ofthe time-series images. That is, by using, as a reference, the frameimage before loading application which was captured by theimage-capturing unit 11, the displacement of the frame image at theinitial time after loading application is calculated. Then, thedisplacement of the frame image at the subsequent time after loadingapplication is calculated, and the displacement of the frame image atthe further subsequent time is calculated, and so on, to calculate thedisplacement from the image before loading application for eachtime-series image. The displacement calculation unit 2 can calculate adisplacement using an image correlation operation. The displacementcalculation unit 2 may also represent a displacement distributiondiagram of the calculated displacement, as a two-dimensional spatialdistribution on the X-Y plane.

The depth moving amount calculation unit 3 calculates a moving amount inwhich a surface of the structure 12 is moved in its normal direction dueto deflection of the structure 12 or the like, from the two-dimensionalspatial distribution of the displacement of the time-series imagecalculated by the displacement calculation unit 2. The depth movingamount calculation unit 3 inputs the calculated moving amount to thedisplacement separation unit 4, the differential displacementcalculation unit 5, and the abnormality determination unit 6.

The displacement separation unit 4 calculates a displacement (referredto as “out-of-plane displacement”) that is based on the moving amountcalculated by the depth moving amount calculation unit 3, which isincluded in the displacement calculated by the displacement calculationunit 2. Further, a displacement (referred to as “in-plane displacement”)caused on a surface of the structure 12 is separated, by subtracting theout-of-plane displacement from the displacement calculated by thedisplacement calculation unit 2 or the displacement distributiondiagram. The displacement separation unit 4 inputs the separatedin-plane displacement to the differential displacement calculation unit5 and the abnormality determination unit 6.

The differential displacement calculation unit 5 performs spatialdifferential on the displacement, the displacement distribution diagram,or the moving amount, and calculates a differential displacementdistribution diagram or a differential moving amount, with thedifferential displacement or the calculated differential displacementbeing a two-dimensional differential spatial distribution on the X-Yplane. The calculation results of the displacement separation unit 4 andthe differential displacement calculation unit 5 are input to theabnormality determination unit 6.

The abnormality determination unit 6 determines the status of thestructure 12 based on the input calculation results. That is, theabnormality determination unit 6 determines the location and type of theabnormality (defect 13) of the structure 12, from the analysis resultsof the three-dimensional spatial distribution information analysis unit7 and the temporal change information analysis unit 8. Further, theabnormality determination unit 6 inputs the determined location and typeof the abnormality of the structure 12, to the abnormality map creationunit 9. The abnormality map creation unit 9 maps the spatialdistribution of the abnormal status of the structure 12 on the X-Yplane, records it as an abnormality map, and outputs the abnormalitymap.

The status determination device 1 can be an information appliance suchas a personal computer (PC) and a server. Each unit that constitutes astatus determination device 1 can be realized by operating a CPU(central processing unit), being an operational resource, and a memoryand an HDD (hard disk drive), being a storage resource, included in theinformation appliance, to operate a program in the CPU.

FIG. 4A to FIG. 4D are diagrams for explaining a relation betweenvarious abnormality statuses of the structure 12 and the in-planedisplacement of the surfaces. FIG. 4A is a side view of the structure 12having a beam-like form supported at two points. As illustrated in FIG.4A, the image-capturing unit 11 as illustrated in FIG. 3 is placed undera condition to capture an image of a lower surface of the structure 12in the image-capturing direction (Z-direction). Under this condition, ifthe structure 12 is in a sound condition, upon application ofperpendicular loading from above the upper surface of the structure 12,a compressive stress is applied onto the upper surface of the structure12, and a tensile stress is applied onto the lower surface thereof, asillustrated in FIG. 4A. Note that the structure 12 is not necessarily abeam-like structure which is supported at two points, as long as similarstresses are exerted on the structure.

Here, when the structure 12 is an elastic body, a stress is proportionalto a strain. Its Young's modulus, being the factor of proportionality,depends on the material of the structure. Because a strain that isproportional to a stress is a displacement per unit length, thedifferential displacement calculation unit 5 can calculate the strain byperforming spatial differential on the result obtained by calculation bythe displacement correction unit 4. That is, a stress field can beobtained by the result of the differential displacement calculation unit5.

As illustrated in FIG. 4B, when there is a crack, the cracked portion issubject to a greater displacement due to loading. On the other hand, nostress is conveyed around the cracked portion, due to the crackedportion. Therefore, the tensile stress at the lower surface of thestructure 12 is smaller than in a sound status illustrated in FIG. 4A.

When there is a separation, the outer appearance of the structure 12when viewed from the lower surface looks similar to as in the case ofcracks, as illustrated in FIG. 4C. However, in case of a separation, nostress is conveyed from the separated portion to the portion above theseparated portion. Therefore, the displacement due to loading at theseparated portion only moves in parallel in a certain amount and in acertain direction, and no strain, being its spatial differential value,will be caused. Accordingly, a crack can be distinguished from aseparation, by using information on the strain obtained by performingspatial differential on the displacement due to loading.

When there is an internal cavity as illustrated in FIG. 4D, theconveyance of a stress is inhibited in the case of internal cavities,and the stress is reduced at the lower surface of the structure 12. Thestrain calculated from the image will accordingly be reduced. Therefore,it is possible to find an internal cavity that cannot be directly foundfrom outside of the structure 12.

The displacement of the structure surface to be measured in FIG. 4A toFIG. 4D is an in-plane displacement (X-direction and Y-direction) withinthe X-Y plane. Therefore, the displacement separation unit 4 calculates,as a correction amount, the apparent displacement (out-of-planedisplacement) based on the moving amount of the surface of the structure12 in the normal direction caused due to the loading applicationcalculated by the depth moving amount calculation unit 3, and subtractsthe out-of-plane displacement therefrom, to separate an in-planedisplacement. The following describes a method to calculate anout-of-plane displacement.

Note that the term “normal line” is used for a curved surface. When asurface has a plurality of small curves, and one large curved surface isformed overall, the normal line is deemed to mean the normal line of thelarge curved surface. Normally, for a plane surface, the term“perpendicular line” is used. However, in the following description, theterm “normal line” is used also in the case of a plane surface, for thesake of simplicity.

FIG. 5 is a diagram for explaining an out-of-plane displacement at thetime of image-capturing a lower surface of the structure, when thestructure 12 is deflected attributed to loading (Please refer to FIG.3). In FIG. 5, the moving amount of the surface of the structure 12 inits normal direction (Z-direction) is deemed to be caused by deflectionof the structure, and is denoted as the amount of deflection δ. Notethat the moving amount of a surface in Z-direction is not limited to theamount of deflection, and can include an amount by which the entirestructure 12 is moved by going downward attributed to loading, forexample.

As illustrated in FIG. 5, when loading causes a deflection (the amountof deflection δ) on the structure 12, in X-direction of theimage-capturing unit 11 on the image-capturing plane, an out-of-planedisplacement δx_(i) is caused due to the amount of deflection δ,separate from Δx_(i) that corresponds to the in-plane displacement Δxbeing the two-dimensional spatial distribution of the displacement ofthe structure surface. Likewise, in Y-direction, Δy_(i) that correspondsto the in-plane displacement Δy and the out-of-plane displacement δy_(i)due to the amount of deflection δ are caused. Let “L” be theimage-capturing distance, let “f” be the lens focal distance, and let(x, y) be the coordinates with its origin being the center ofimage-capturing on the structure surface. Then, the out-of-planedisplacement δx_(i) δy_(i), and the in-plane displacement Δx_(i), Δy_(i)are respectively represented as in the following Expressions 1, 2, 3,and 4.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 1} \rbrack & \; \\{{\delta\; x_{i}} = {{f( {\frac{1}{L - \delta} - \frac{1}{L}} )}x}} & ( {{Expression}\mspace{14mu} 1} ) \\\lbrack {{Math}.\mspace{14mu} 2} \rbrack & \; \\{{\delta\; y_{i}} = {{f( {\frac{1}{L - \delta} - \frac{1}{L}} )}y}} & ( {{Expression}\mspace{14mu} 2} ) \\\lbrack {{Math}.\mspace{14mu} 3} \rbrack & \; \\{{\Delta\; x_{i}} = {\frac{f}{L - \delta}\Delta\; x}} & ( {{Expression}\mspace{14mu} 3} ) \\\lbrack {{Math}.\mspace{14mu} 4} \rbrack & \; \\{{\Delta\; y_{i}} = {\frac{f}{L - \delta}\Delta\; y}} & ( {{Expression}\mspace{14mu} 4} )\end{matrix}$

For example, when the amount of deflection δ after loading on thestructure 12 compared to before loading is 4 mm, the image-capturingdistance L is 5 m, and the lens focal distance f is 50 mm, and when thedistance x from the image-capturing center on the surface of thestructure 12 is 200 mm, the out-of-plane displacement δx_(i) of theimage-capturing plane is 1.6 μm, from Expression 1. When there is anin-plane displacement Δx of 160 μm on the surface of the structure 12,the in-plane displacement Δx_(i), of the image-capturing plane is 1.6μm, from Expression 3. In this way, an out-of-plane displacement equalto an in-plane displacement is likely superposed on the displacement ofthe time-series images calculated by the displacement calculation unit 2and the displacement distribution diagram depicting the two-dimensionalspatial distribution on the X-Y plane.

Here, by summarizing Expression 1 and Expression 2 as an out-of-planedisplacement vector δi(δx_(i), δy_(i)); and Expression 3 and summarizingExpression 4 as an in-plane displacement vector Δi(Δx_(i), Δy_(i)), thefollowing Expression 5 and Expression 6 result.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 5} \rbrack & \; \\{{\delta\;{i( {{\delta\; x_{i}},{\delta\; y_{i}}} )}} = ( {{{f( {\frac{1}{L - \delta} - \frac{1}{L}} )}x},{{f( {\frac{1}{L - \delta} - \frac{1}{L}} )}y}} )} & ( {{Expression}\mspace{14mu} 5} ) \\\lbrack {{Math}.\mspace{14mu} 6} \rbrack & \; \\{{\Delta\;{i( {{\Delta\; x_{i}},{\Delta\; y_{i}}} )}} = ( {{\frac{f}{L - \delta}\Delta\; x},{\frac{f}{L - \delta}\Delta\; y}} )} & ( {{Expression}\mspace{14mu} 6} )\end{matrix}$

FIG. 6 is a diagram illustrating the relationship between anout-of-plane displacement vector δi(δx_(i), δy_(i)) and an in-planedisplacement vector Δi(Δx_(i), Δy_(i)), which are represented byExpression 5 and Expression 6. In FIG. 6, the out-of-plane displacementvector δi(δx_(i), δy_(i)) is a radial vector group (the thin solid arrowin FIG. 6), and its magnitude R (x, y) is expressed as Expression 7,from Expression 1 and Expression 2. In Expression 7, if the amount ofdeflection δ is constant, its magnitude takes a value proportional tothe distance from the image-capturing center. Let “k” be the factor ofproportionality as denoted in Expression 8, Expression 7 can beexpressed as Expression 9.

$\begin{matrix}{\mspace{79mu}\lbrack {{Math}.\mspace{14mu} 7} \rbrack} & \; \\{{R( {x,y} )} = {\sqrt{{\delta\;{x_{i}( {x,y} )}^{2}} + {\delta\;{y_{i}( {x,y} )}^{2}}} = {{f( {\frac{1}{L - \delta} - \frac{1}{L}} )}\sqrt{x^{2} + y^{2}}}}} & ( {{Expression}\mspace{14mu} 7} ) \\{\mspace{79mu}\lbrack {{Math}.\mspace{14mu} 8} \rbrack} & \; \\{\mspace{79mu}{k = {f( {\frac{1}{L - \delta} - \frac{1}{L}} )}}} & ( {{Expression}\mspace{14mu} 8} ) \\{\mspace{79mu}\lbrack {{Math}.\mspace{14mu} 9} \rbrack} & \; \\{\mspace{79mu}{{R( {x,y} )} = {k\sqrt{x^{2} + y^{2}}}}} & ( {{Expression}\mspace{14mu} 9} )\end{matrix}$

Here, the displacement distribution calculated by the displacementcalculation unit 2 corresponds to a measurement vector V(Vx, Vy) (thedotted arrow in FIG. 6), which is a resultant vector between theout-of-plane displacement vector δi(δx_(i), δy_(i)) (the thin solidarrow in FIG. 6) and the in-plane displacement vector Δi(Δx_(i), Δy_(i))(the bold solid arrow in FIG. 6). Let Rmes(x, y) be the magnitude of themeasurement vector V(Vx, Vy). Then, Expression 10 and Expression 11result.[Math. 10]Rmes(x,y)=√{square root over (Vx(x,y)² +Vy(x,y)²)}  (Expression 10)[Math. 11]V(V _(x) ,V _(y))=Δi(Δx _(i) ,Δy _(i))+δi(δx _(i) ,δy _(i))  (Expression11)

FIG. 7A and FIG. 7B are graphs depicting an example of the value of themagnitude R(x, y) of the out-of-plane displacement vector δi(δx_(i),δy_(i)) given by Expression 7, Expression 8, and Expression 9. FIG. 7Aand FIG. 7B are graphs depicting the magnitude R(x, y) of theout-of-plane displacement vector when the amount of deflection δ is 1 mmand 4 mm, respectively. In each graph, the image-capturing distance Lbefore deflection is 5000 mm, and the focal distance f is 50 mm. As canbe understood by comparing the graphs of FIG. 7A and FIG. 7B, bothgraphs are similar figures to each other, and as the amount ofdeflection δ is larger, its enlargement factor increases. Thisenlargement factor corresponds to the factor of proportionality K givenby Expression 8.

FIG. 8 is a graph in which the magnitude Rmes(x, y) of the measurementvector V(Vx, Vy) is superposed on the graph in FIG. 7B. In FIG. 8,Rmes(x, y) is expressed by a thin solid line. Rmes(x, y) takes a formsimilar to the magnitude R(x, y) of the out-of-plane displacementvector, if the magnitude R(x, y) of the out-of-plane displacement vectoris larger than the in-plane displacement vector Δi(Δx_(i), Δy_(i)), andtherefore the enlargement factor of R(x, y) can be estimated fromRmes(x, y). The enlargement factor of R(x, y) is estimated by obtainingthe factor of proportionality k at which the evaluation function E(k)depicted in Expression 12 is minimized.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 12} \rbrack & \; \\{{E(k)} = {\sum\limits_{x,y}^{\;}\{ {{R_{mes}( {x,y} )} - {R( {x,y} )}} \}^{2}}} & ( {{Expression}\mspace{14mu} 12} )\end{matrix}$

The intensity factor k in Expression 12 is calculated by theleast-square method. The evaluation function E(k) may be sum of absolutevalues, other power sums, and the like, other than the sum of squares ofthe difference between Rmes(x, y) and R(x, y).

The displacement separation unit 4 estimates the out-of-planedisplacement vector by performing an operation to convert the estimatedenlargement factor k into an amount of deflection δ using Expression 8,to estimate the out-of-plane displacement vector. The displacementseparation unit 4 further extracts an in-plane displacement vector, bysubtracting the out-of-plane displacement vector as a correction amount,from the measurement vector obtained by the displacement calculationunit 2.

The following explains an example in which the in-plane displacement isextracted by calculating the out-of-plane displacement, and subtractingthe calculated out-of-plane displacement from the measured displacement,taking an example in which the structure 12 has a crack alongY-direction as illustrated in FIG. 4B. In calculating a displacement bymeans of the displacement calculation unit 2, the time-series imagesobtained by image-capturing the lower surface of the structure 12illustrated in FIG. 3 in the image-capturing direction illustrated inthis drawing before and after loading application are used.

Here, the image-capturing distance is set to be 5 m, and the structure12 is assumed to be a double-supported beam under the conditionequivalent to when 10 tons of loading is applied, which is made ofconcrete (Young's modulus of 40 GPa) and has a length of 20 m, athickness of 0.5 m, and a width of 10 m. The area of the image at whichthe displacement is measured is assumed to be in the range of ±200 mmboth in X-direction and Y-direction, with the cracked portion of thesurface of the structure 12 serving as the image center.

An example assumes the lens focal distance of the camera of theimage-capturing unit 11 to be 50 mm and the pixel pitch to be 5 μm, soas to obtain pixel resolution of 250 μm at the image-capturing distanceof 5 m. The image-capturing element of the image-capturing unit 11 ismonochroic and has 2000 pixels horizontally and 2000 pixels vertically,to enable image-capturing the range of 0.5 m×0.5 m at theimage-capturing distance of 5 m. The frame rate of the image-capturingelement is assumed to be 60 Hz. In addition, in the displacementcalculation unit 2, the image correlation is conducted by sub-pixeldisplacement estimation by quadratic curve interpolation, to enabledisplacement estimation up to 1/100 pixels, and 2.5 μm displacementresolution.

When the above-described image-capturing unit 11 is used, the imagedisplacement measurement area (in the range of −200 mm to 200 mm in bothX-direction and Y-direction) will have 1600 pixels horizontally and 1600pixels vertically. For this pixel area, the operations of Expression 1to Expression 12 are conducted.

FIG. 9A and FIG. 9B illustrate a displacement distribution inX-direction of the measurement vector V(Vx, Vy) when Y=0 mm and adisplacement distribution in Y-direction when X=0 mm, which have beenobtained by the displacement calculation unit 2, respectively. FIG. 9Aand FIG. 9B are graphs in which the displacement obtained fromExpression 6 is the displacement in the coordinates on the surface ofthe structure 12 to be measured, which do not take into considerationthe out-of-plane displacement contained in the measurement vector V(Vx,Vy).

In FIG. 9A illustrating a displacement in X-direction, the displacementof ±170 μm is caused in the range of ±200 mm from the image capturingrange. In FIG. 9B illustrating a displacement in Y-direction, thedisplacement of ±160 μm is caused as a straight line, in the range of±200 mm from the image capturing range. The displacement in X-directionis a displacement on which the out-of-plane displacement is superposedon the in-plane displacement. On the other hand, the displacement inY-direction is a displacement with only the out-of-plane displacement.

The factor of proportionality k at which the evaluation function E(k) inExpression 12 is minimized is obtained as 0.000008 using the measurementvector V(Vx, Vy) obtained in the displacement calculation unit 2 in theleast-square method. When substituting this value in Expression 8, theamount of deflection δ is obtained to be 4 mm, as an output of thecorrection amount calculation unit 3.

By substituting this amount of deflection δ in Expression 5, theout-of-plane displacement vector δi(δx_(i), δy_(i)) is obtained in thedisplacement separation unit 4. The displacement separation unit 4further obtains the in-plane displacement vector Δi(Δx_(i), Δy_(i)) bysubtracting this out-of-plane displacement vector δi(δx_(i), δy_(i))from the measurement vector V(Vx, Vy) obtained in the displacementcalculation unit 2, and calculates the in-plane displacements forX-direction and Y-direction from Expression 6.

FIG. 10A and FIG. 10B illustrate an output of the displacementseparation unit 4. FIG. 10A is a graph depicting a displacement inX-direction, which illustrates occurrence of a steep and discontinuousdisplacement of 20 μm in the cracked portion. On the other hand, FIG.10B is a graph depicting a displacement in Y-direction, in which thedisplacement is 0. As in FIG. 10A and FIG. 10B, the in-planedisplacement on the structure surface can be extracted by beingseparated from the out-of-plane displacement.

FIG. 11 is a diagram for explaining a case where there is a tilt in thestructure 12, in a calculation method of an out-of-plane displacement.As illustrated in FIG. 11, when the vertical line on the surface of thestructure 12 is rotated by θ with Y-axis serving as an axis, therelation between the coordinates with z-axis being the optical axis ofthe image-capturing unit 11 and the coordinates with the normal line ofthe structure surface being z′ is expressed by Expression 13, Expression14, and Expression 15.[Math. 13]x′=x*cos θ+z*sin θ  (Expression 13)[Math. 14]y′=y  (Expression 14)[Math. 15]z′=−x*sin θ+z*cos θ  (Expression 15)

The X-Y coordinates of the image surface rotated by θ are mapped usingExpression 16 and Expression 17.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 16} \rbrack & \; \\{X = ( \frac{x^{\prime}*f}{L - z^{\prime}} )} & ( {{Expression}\mspace{14mu} 16} ) \\\lbrack {{Math}.\mspace{14mu} 17} \rbrack & \; \\{Y = ( \frac{y^{\prime}*f}{L - z^{\prime}} )} & ( {{Expression}\mspace{14mu} 17} )\end{matrix}$

Consequently, the out-of-plane displacement δx_(i) in X-direction andthe out-of-plane displacement δy_(i) in Y-direction, attributed todisplacement from the coordinates P1(x1, y1, z1) to the coordinatesP2(x2, y2, z2) by deflection of the structure 12 due to loadingapplication, are expressed by Expression 18 and Expression 19,respectively (FIG. 11 does not illustrate the Y-component).

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 18} \rbrack & \; \\{{\delta\;{xi}} = {{{x\; 2i} - {x\; 1i}} = {( \frac{x\; 2*f}{L - {z\; 2}} ) - ( \frac{x\; 1*f}{L - {z\; 1}} )}}} & ( {{Expression}\mspace{14mu} 18} ) \\\lbrack {{Math}.\mspace{14mu} 19} \rbrack & \; \\{{\delta\;{yi}} = {{{y\; 2i} - {y\; 1i}} = {( \frac{{y2}*f}{L - {z\; 2}} ) - ( \frac{y\; 1*f}{L - {z\; 1}} )}}} & ( {{Expression}\mspace{14mu} 19} )\end{matrix}$

Therefore, if there is a tilt θ, the function R(θ) is obtained bysubstituting Expression 18 and Expression 19 into Expression 7. Here,when the tilt angle θ is unknown, the function R(θ) is used for eachangle θ to obtain k(θ) at which the evaluation function E(k) inExpression 12 is minimized, by changing θ for example by 0.5° from 0° to90°. Then, from among all the obtained k(θ), the angle at which theevaluation function E(k) is minimized is set to be the tilt angle. Fromthe relation between “k” in this tilt angle and Expression 8, the amountof deflection δ is obtained. From the relation among the obtained tiltangle, the obtained amount of deflection δ, and Expressions 13, 14, 15,16, 17, 18, and 19, the out-of-plane displacement vector δi(δx_(i),δy_(i)) can be estimated.

This result is input to the displacement separation unit 4 as an outputfrom the depth moving amount calculation unit 3. The displacementseparation unit 4 obtains the in-plane displacement vector Δi(Δx_(i),Δy_(i)) by subtracting the out-of-plane displacement vector δi(δx_(i),δy_(i)) from the measurement vector V(Vx, Vy). Here, the in-planedisplacement of the structure can be obtained by calculating theprojection onto the surface after loading application with respect tothe in-plane displacement vector Δi(Δx_(i), Δy_(i)) using Expressions13, 14, 15, 16, and 17.

FIG. 11 deals with a case in which, where Y-axis serves as an axis, thenormal line of the surface of the structure 12 is rotated by θ withrespect to the optical axis in the center of the image-capturingdirection of the image-capturing unit 11. However, correction is alsopossible in cases where X-axis or Z-axis serves as an axis.

The in-plane displacement on the structure surface, being the output ofthe displacement separation unit 4, is replaced with the strain on thestructure surface in the differential displacement calculation unit 5.By multiplying the strain on the structure surface by a Young's modulus,the stress will result. Accordingly, the stress field on the structuresurface is obtained. The displacement information obtained by thedisplacement separation unit 4, the strain information obtained by thedifferential displacement calculation unit 5, and the moving amountobtained by the depth moving amount calculation unit 3 are input to theabnormality determination unit 6.

The abnormality determination unit 6 identifies the type and location ofa defect based on the displacement information obtained by thedisplacement separation unit 4, the strain information obtained by thedifferential displacement calculation unit 5, and the moving amountobtained by the depth moving amount calculation unit 3. To do this, theabnormality determination unit 6 includes, in advance, a threshold valuefor determining a defect, and patterns of a characteristic displacementand strain for the type of defect, in the three-dimensional spatialdistribution information analysis unit 7 and the temporal changeinformation analysis unit 8. The three-dimensional spatial distributioninformation analysis unit 7 and the temporal change information analysisunit 8 thereby determine the sound status or a defect such as a crack, aseparation, and an internal cavity, as illustrated in FIG. 4A to FIG.4D, by comparing the displacement information, the strain information,or the moving amount with the threshold value or by means of patternmatching with the pattern.

In the following explanation, the operation performed by the abnormalitydetermination unit 6 is explained in the following order. First, thedetermining operation (X-direction and Y-direction) for the displacementinformation obtained by the displacement separation unit 4, and thestrain information obtained by the differential displacement calculationunit 5 is explained, and then the determining operation (Z-direction)for the moving amount obtained by the depth moving amount calculationunit 3 is explained.

First, the determining operation (X-direction and Y-direction) for thedisplacement information obtained by the displacement separation unit 4,and the strain information obtained by the differential displacementcalculation unit 5 is explained.

FIG. 10A illustrates an example of an in-plane displacement on a surfaceof a structure in X-direction due to loading application when there is acrack along Y-direction. It can be understood that a steep anddiscontinuous in-plane displacement of 20 μm is generated in the crackedportion. Such a sudden displacement will not be generated in a soundstatus without defects. Therefore, by providing a threshold value for asize of a discontinuous displacement in advance, a crack can be detectedwhen a displacement exceeding this is confirmed.

FIG. 12A and FIG. 12B illustrate a distribution of a stress field arounda cracked portion calculated by the differential displacementcalculation unit 5 when there is a crack along Y-direction. Asillustrated in FIG. 12A, the direction of the stress will be bent by thecrack. Therefore, even when there is a tensile stress exerted on bothends of the structure in X-direction in FIG. 12A, a Y-directioncomponent will be generated in the direction of the stress in thevicinity of the crack as illustrated in FIG. 12B. Therefore, a crack canalso be detected by detecting whether there is this Y-directioncomponent. Note that a distribution of such a stress field around acrack is known as a stress intensity factor in an elastic body whichexhibits a linear response, and thus such information can also be used.

FIG. 13A to FIG. 13D illustrate an example of a two-dimensionaldisplacement distribution of a displacement amount around a crack. FIG.13A and FIG. 13B are a contour of a displacement amount in a directionhorizontal (X-direction) in FIG. 4B and in a direction vertical(Y-direction) to the paper in which the drawing is drawn in FIG. 4B. Asillustrated in FIG. 13A, in X-direction, the contour of the displacementamount is less dense around a crack than in the area without cracks.This corresponds to the portion of a moderate displacement outside thesteep displacement in the cracked portion illustrated in FIG. 10A. Thedisplacement in this portion is more moderate than the displacementwithout cracks.

As illustrated in FIG. 13B, in Y-direction, a Y-direction component of adisplacement is generated in an area around the cracked portion. Thiscorresponds to the Y-direction component in the stress field (strain)illustrated in FIG. 12B.

FIG. 13C and FIG. 13D each illustrate a case in which a crack is deeperthan in the cases of FIG. 13A and FIG. 13B. In these cases, the contourof the displacement amount is less dense in an area around a crack ineach of X-direction and Y-direction. It is also possible to know thedepth of a crack, from this density information.

The determination of a crack as described above is performed in thetwo-dimensional spatial distribution information analysis unit 7 in theabnormality determination unit 6 in FIG. 2.

When there is a crack, as the crack is wider open, the displacementamount will increase sharply in the cracked portion, as illustrated inFIG. 10A. Therefore, by preparing each threshold value for thedisplacement amounts per unit length in X-direction or Y-direction, itis possible to expect a crack at a location where the displacementamount that exceeds the threshold value is detected.

In addition, the strain in X-direction becomes rapidly large at thecracked portion. For this reason, by preparing a threshold value for thestrain value in X-direction, it is possible to expect a crack at alocation where a strain that exceeds the threshold value is detected.

Furthermore, as illustrated in FIG. 12A and FIG. 12B, when there is acrack, a strain in Y-direction is caused. Therefore, by preparing athreshold value for the strain value in Y-direction, it is possible toexpect a crack at a location where a strain that exceeds the thresholdvalue is detected.

Each threshold value described above can be set by a simulation using asize or a material similar to those of the structure, an experimentusing a reduced-size model, and the like. The threshold value can alsobe set by measuring the actual structure for a long period of time andaccumulating the data.

The above-described determination can also be performed by patternmatching processing as described below, not limited to theabove-described numerical comparison.

FIG. 14A to FIG. 14C are a diagram illustrating pattern matchingprocessing of a displacement distribution by the three-dimensionalspatial distribution information analysis unit 7. By using thedisplacement separation unit 4 and the differential displacementcalculation unit 5, the displacement amount can be represented as adisplacement distribution diagram on the X-Y plane, as illustrated inFIG. 13A to FIG. 13D. As illustrated in FIG. 14A, the three-dimensionalspatial distribution information analysis unit 7 rotates, or scales upor down the pattern in X-direction of the displacement around the crackhaving been stored in advance, subjects the same to pattern matchingwith the displacement distribution diagram obtained in the displacementseparation unit 4, to determine the direction and depth of the crack.Here, the pattern in X-direction of the displacement around the crackhaving been stored in advance may be created in advance by simulation orthe like, for each depth or width of a crack.

In addition, as illustrated in FIG. 14B, the three-dimensional spatialdistribution information analysis unit 7 rotates, or scales up or downthe pattern in Y-direction of the displacement around the crack havingbeen stored in advance, subjects the same to pattern matching with thedisplacement distribution diagram obtained in the displacementseparation unit 4, to determine the direction and depth of the crack.Here, the pattern in Y-direction of the displacement around the crackhaving been stored in advance may be created in advance by simulation orthe like, for each depth or width of a crack.

In addition, as illustrated in FIG. 14C, the three-dimensional spatialdistribution information analysis unit 7 rotates, or scales up or downthe pattern of the differential vector field of the displacement aroundthe crack having been stored in advance, subjects the same to patternmatching with the differential vector field (corresponding to a stressfield) obtained in differential displacement calculation unit 5, todetermine the direction and depth of the crack. Here, the pattern of thedifferential vector field of the displacement around the crack havingbeen stored in advance may be created in advance by simulation or thelike, for each depth or width of a crack.

A correlation operation is used in the pattern matching. The patternmatching may be performed using various other statistical operationalapproaches.

So far, the cases in which the structure 12 has a crack have beendescribed. As follows, the cases in which the structure 12 has aninternal cavity and the cases in which the structure 12 has a separationare described.

FIG. 15A and FIG. 15B illustrate a two-dimensional distribution of astress on a surface viewed along the image-capturing direction whenthere is an internal cavity as illustrated in FIG. 4D, where FIG. 15A isa perspective view and FIG. 15B is a plan view. As illustrated in FIG.15B, loading causes a stress exerted in X-direction in the drawing.However, in the cavity portion, the stress field is bent, to causes thestress to contain a component in Y-direction as illustrated in thedrawing.

FIG. 16A to FIG. 16C are diagrams illustrating a contour and a stressfield of a displacement of a surface viewed along the image-capturingdirection when there is an internal cavity. FIG. 16A illustrates acontour of an X-component of the displacement, FIG. 16B illustrates acontour of a Y-component of the displacement, and FIG. 16C illustrates astress field.

As illustrated in the description about FIG. 4D, a strain amount issmall in a cavity portion. Therefore, the density of the contour of theX-component of the displacement illustrated in FIG. 16A is small. Thecontour of the Y-component of the displacement illustrated in FIG. 16Btakes a form of a closed curve. Further, the stress field, which is adifferential of the displacement and is illustrated in FIG. 16C, is bentat the cavity portion. The effect of the stress field on the surfacegets more noticeable when the cavity portion is closer to the surface.Therefore, the depth of a cavity portion from the surface can also beestimated from how the stress field is bent.

Here, just as when a crack is determined, by replacing FIG. 14A withFIG. 16A, FIG. 14B with FIG. 16B, and FIG. 14C with FIG. 16C, withrespect to the pattern in X-direction of the displacement around thecavity, the pattern in Y-direction of the displacement around thecavity, and the differential vector field (corresponding to a stressfield), which have been stored in advance in the three-dimensionalspatial distribution information analysis unit 7, the statusdetermination of the location and depth of the internal cavity can beperformed. The pattern matching uses a correlation operation. Thepattern matching may be performed using various other statisticaloperational approaches.

In case of internal cavity, too, by preparing a threshold value for thedisplacement amount in Y-direction and the strain in Y-direction basedon the characteristics of these displacement amount and strain, it ispossible to expect an internal cavity when the threshold value isexceeded.

FIG. 17A and FIG. 17B are diagrams for explaining a response whenshort-term loading (referred to as “impulse stimulation”) is appliedonto a structure having an internal cavity. The impulse stimulation canbe applied on a location to be applied with loading, for example. FIG.17B illustrates a time response of displacement at each point A, B, C ona surface illustrated in FIG. 17A in response to this impulsestimulation. At point A with no internal cavity, the stress is conveyedfast, and the amplitude of displacement is great. At point C, however,since the stress is not conveyed within the internal cavity but isconveyed from around the cavity, the stress is conveyed slowly and theamplitude of the displacement is small. At point B, which is halfwaythrough point A and point C, the stress conveyance time and amplitudeare the values between those of point A and point C. Therefore, when thedisplacement distribution within the plane when the structure is viewedalong the image-capturing direction is subject to frequency analysis inthe temporal change information analysis unit 8 in the abnormalitydetermination unit 6, the area of the internal cavity can be identified,from the amplitude and the phase near the resonant frequency. Aninternal cavity may be determined by the shift in the resonantfrequency.

Note that even when loading is applied for a long period of time, in theinitial stage of loading application, the fluctuation in displacement,which corresponds to FIG. 17B, will be confirmed. In this case, however,the value at which the displacement converges is not zero, but is avalue balanced with loading. Therefore, even when loading is applied fora long period of time, the temporal change information analysis unit 8can still identify the area of the internal cavity.

The temporal change information analysis unit 8 performs theabove-described displacement time response processing by frequencyanalysis using fast Fourier transform. The frequency analysis may beperformed by various types of frequency analysis approaches, such aswavelet transform.

FIG. 18A to FIG. 18C are diagrams illustrating a contour and a stressfield of a displacement of a surface viewed along the image-capturingdirection when there is a separation. FIG. 18A illustrates a contour ofan X-component of the displacement, FIG. 18B illustrates a contour of aY-component of the displacement, and FIG. 18C illustrates a stressfield.

As illustrated in FIG. 4C, when there is a separation, the outerappearance similar to that of a crack is observed when viewed from thelower surface of the beam-like structure. However, no stress is conveyedfrom the separated portion to the portion above the separated portion;therefore, at the separated portion, the displacement after loadingcompared to before loading only moves in parallel in a certain amountand in a certain direction, and no strain, being its spatialdifferential value, will be caused.

FIG. 18A illustrates a contour of an X-component of a displacement. Theseparated portion does not have a contour because there is no strain andmoves in a certain direction. Using this characteristic, the abnormalitydetermination unit 6 determines that there is a separation. The portioncorresponding to point A in the drawing is a cleavage due to aseparation, at which a stress is hardly conveyed, and has a less densecontour than in point B which is a sound portion. The abnormalitydetermination unit 6 may use this characteristic to distinguish betweenthe separated portion and the sound portion.

FIG. 18B illustrates a contour of a Y-component of a displacement. AY-direction displacement is caused at a portion outside the separatedportion. Using this characteristic, the abnormality determination unit 6can determine that there is a separation. In addition, the stress fieldthat is a differential of the displacement illustrated in FIG. 18C takeseither 0 or a value near 0 at the separated portion. The abnormalitydetermination unit 6 may use this characteristic to determine that thereis a separation.

Here, just as when the depth of a crack is determined, by replacing FIG.14A with FIG. 18A, FIG. 14B with FIG. 18B, and FIG. 14C with FIG. 18C,with respect to the pattern in X-direction of the displacement aroundthe separation, the pattern in Y-direction of the displacement aroundthe cavity, and the differential vector field (corresponding to a stressfield), which have been stored in advance in the three-dimensionalspatial distribution information analysis unit 7, the location of theseparation can be determined. The pattern matching uses a correlationoperation. The pattern matching may be performed using various otherstatistical operational approaches.

FIG. 19 is a diagram illustrating a time response when the structurehaving a separation is subject to an impulse stimulation. In the timeresponse, the separated portion has a displacement that is reverse tothat of the sound portion; that is, the separated portion takes awaveform whose phase is 180° different from the sound portion. Inaddition, the separated portion has a great amplitude because of beinglight. When the displacement distribution within the plane when thestructure is viewed along the image-capturing direction is subject tofrequency analysis in the temporal change information analysis unit 8,the separated portion can be identified based on the amplitude and thephase. Moreover, because of being separated away from the entirestructure, a separated portion likely include a frequency componentdifferent from that of the entire structure. Therefore, a separatedportion may be determined by the shift in the resonant frequency.

In the above processing, the temporal change information analysis unit 8performs frequency analysis using fast Fourier transform. The frequencyanalysis may be performed by various types of frequency analysisapproaches, such as wavelet transform.

Next, the determining operation (Z-direction) for the moving amountobtained by the depth moving amount calculation unit 3 and thedifferential value of the moving amount is explained.

FIG. 20A and FIG. 20B are diagrams illustrating how a structure isdeflected due to loading, and FIG. 20A illustrates a sound case, andFIG. 20B illustrates a deteriorated case. When a structure is lesselastic due to aging or the like, the amount of deflection in thedeteriorated status as illustrated in FIG. 20B is greater than in thesound status as illustrated in FIG. 20A. Therefore, by providing athreshold value for the amount of deflection by attributing the movingamount calculated by the depth moving amount calculation unit 3 to theamount of deflection, a case of deterioration can be determined when themoving amount exceeds this threshold value. This threshold value can beobtained by converting the amount of deflection when predeterminedloading is applied, based on the calculation of strength performed indesigning a structure, for example.

The three-dimensional spatial distribution information analysis unit 7of the abnormality determination unit 6 compares the above-mentionedmoving amount and the threshold value, to determine a case ofdeterioration. Not necessarily limited to a simple deflection asillustrated in FIG. 20A and FIG. 20B, the distribution of a structuremay be distributed in the horizontal direction (X-direction). FIG. 21Aand FIG. 21B are to explain an example of the above-mentioneddetermination in the three-dimensional spatial distribution informationanalysis unit 7, which explains the processing when deflections aredistributed in X-direction.

As illustrated in FIG. 21A, the image-capturing range is divided intonine areas, i.e., from area A to area I, for example. By obtaining eachfactor of proportionality k that minimizes the evaluation function E(k)in Expression 12 for each area, the amount of deflection in each area(i.e. moving amount which is a displacement amount in Z-direction) iscalculated (FIG. 21B). For example, the amount of deflection in eacharea can be represented by the amount of deflection in the center ofeach area, as illustrated in FIG. 21B. By comparing the amount ofdeflection in each area with the threshold value of the amount ofdeflection pre-set for each area, it is possible to determine thedeteriorated area. Note that the number of divisions and the area sizeconcerning the divided areas can be freely set.

FIG. 22 is a diagram illustrating a change of a moving amount (amount ofdeflection) from a start to an end of the loading application. FIG. 22illustrates a temporal change of the moving amount in area B of FIG.21A. From the temporal change of the moving amount, the maximum value ofthe moving amount can be set as the amount of deflection, for example.By comparing this amount of deflection with the threshold value, it ispossible to determine a case of deterioration. Note that the temporalchange of the moving amount can be recorded for each area.

FIG. 23 is a diagram illustrating a distribution of a characteristicdeflection when there is a cavity inside a structure. The distributionof a deflection when there is an internal cavity inside a structure issuch that the displacement is smaller on the surface at which aninternal cavity exists, than in the distribution of a deflection whenthere is no internal cavity (the distribution illustrated by the brokenline in the drawing). By recording this characteristic straindistribution in advance, the three-dimensional spatial distributioninformation analysis unit 7 can determine an existence of an internalcavity, from the obtained distribution of a deflection.

In addition, based on the change of the moving amount in FIG. 22, adifferential value that would result by performing spatial differentialon a moving amount which is a displacement amount in the differentialdisplacement calculation unit 5 can be obtained. A differential value ofa moving amount represents a strain in Z-direction. Therefore, by thethree-dimensional spatial distribution information analysis unit 7storing, in advance, a characteristic difference between a strain inZ-direction when there is an internal cavity and a strain when there isno internal cavity, an existence of an internal cavity can be determinedalso from a strain in Z-direction.

In addition, the temporal change information analysis unit 8 candetermine a case of deterioration such as aging, from a temporal changeof a moving amount. That is, when a structure ages, a period of a changeof a moving amount when loading is applied gets long. Therefore, byproviding, in advance, a threshold value for a period of change of amoving amount, it is possible to determine that a structure is aged whenthe period exceeds the threshold value. A period of a change of adifferential value of a moving amount can also be used to determine acase of deterioration, similarly to the above.

FIG. 24 is a flowchart illustrating a status determination method of thestatus determination device 1 as illustrated in FIG. 2.

In Step S1, among the time-series images of the surface of the structure12 before and after the loading application which have been captured bythe image-capturing unit 11, the displacement calculation unit 2 in thestatus determination device 1 takes in a frame image before loadingapplication which serves as a reference in calculating a displacementamount after the loading application compared to before the loadingapplication, and further takes in frame images after the loadingapplication in time series.

The displacement calculation unit 2 calculates displacement amounts inX, Y-directions of the image after the loading application with respectto the image before the loading application which serves as a reference.A displacement distribution diagram (a contour of the displacementamount) may also be drawn in which the two-dimensional distribution ofthe calculated displacement amounts is displayed on the X-Y plane. Thedisplacement calculation unit 2 inputs the calculated displacementamount or the displacement distribution diagram, to the depth movingamount calculation unit 3 and the displacement separation unit 4.

In Step S2, from the two-dimensional spatial distribution of thedisplacement of the time-series images calculated by the displacementcalculation unit 2, the depth moving amount calculation unit 3calculates a moving amount in which the surface of the structure 12 hasmoved in its normal direction by deflection of the structure 12 due toloading or the like. During this process, the depth moving amountcalculation unit 3 estimates a tilt angle formed by the optical axis ofthe image-capturing unit 11 and the normal line of the surface of thestructure 12, and calculates a moving amount which takes into accountthis tilt angle. The depth moving amount calculation unit 3 inputs thuscalculated moving amount to the displacement separation unit 4, thedifferential displacement calculation unit 5, and the abnormalitydetermination unit 6.

In Step S3, the displacement separation unit 4 calculates anout-of-plane displacement based on the moving amount.

In Step S4, the displacement separation unit 4 separates the in-planedisplacement by subtracting the out-of-plane displacement from thedisplacement amount obtained in the displacement calculation unit 2.That is, the displacement separation unit 4 calculates the in-planedisplacement in the X-Y direction of the surface of the structure 12after loading application, with respect to before the loadingapplication which serves as a reference. A displacement distributiondiagram (a contour of the displacement amount) may also be drawn inwhich the two-dimensional distribution of the calculated in-planedisplacements is displayed on the X-Y plane. The displacement separationunit 4 inputs the calculated result, to the differential displacementcalculation unit 5 and the abnormality determination unit 6.

In Step S5, the differential displacement calculation unit 5 subjectsthe in-plane displacement or the displacement distribution diagram inputby the displacement separation unit 4 to spatial differentialprocessing, to calculate a differential displacement amount (stressvalue) or a differential displacement distribution diagram (stressfield). The differential displacement calculation unit 5 calculates adifferential displacement amount (stress value) or a differentialdisplacement distribution diagram (stress field) of a depth movingamount obtained in the depth moving amount calculation unit 3. Thedifferential displacement calculation unit 5 inputs the calculatedresults to the abnormality determination unit 6.

The following Step S6, Step S7, Step S8, and Step S9 are steps in whichthe three-dimensional spatial distribution information analysis unit 7of the abnormality determination unit 6 determines a crack, aseparation, an internal cavity, and a deterioration, being a defect of astructure. As a determination method, the pattern matching method andthe method by way of a threshold value, having been described above, aretaken as an example.

In Step S6, the three-dimensional spatial distribution informationanalysis unit 7 of the abnormality determination unit 6 determines thestatus of a crack, a separation, or an internal cavity, from thedisplacement amount or the displacement distribution diagram inX-direction having been input.

First, the determination method by way of pattern matching is described.The three-dimensional spatial distribution information analysis unit 7includes, as a database, a displacement distribution pattern created inadvance corresponding to a width, a depth, or the like of a crack, aninternal cavity, or a separation as illustrated in FIG. 14A, FIG. 16A,and FIG. 18A. The three-dimensional spatial distribution informationanalysis unit 7 performs pattern matching, by rotating or scaling up ordown these displacement distribution patterns with respect to thedisplacement distribution diagram in X-direction input by thedisplacement separation unit 4, thereby determining the location or typeof the defect on the X-Y plane.

Next, the determining method by way of a threshold value of adisplacement amount is described. The three-dimensional spatialdistribution information analysis unit 7 determines, for example,continuity of the displacement amount based on the displacement amountin X-direction having been input. That is, as illustrated in FIG. 10A,whether there is continuity is determined based on whether there is asudden change of a threshold value or above in the displacement amount.When there is a sudden change suggesting no continuity in any part onthe X-Y plane, the three-dimensional spatial distribution informationanalysis unit 7 determines that there is a possibility of a crack or aseparation existing in that part, and sets a discontinuity flag DisC(x,y, t) to 1, and records, as numerical value information, thedisplacement amount data for the portion subject to the sudden change.Here, “t” indicates a time of the frame image taken in Step S1 on thetime-series images.

The abnormality determination unit 6 inputs, to the abnormality mapcreation unit 9, information on the defect determined by the patternmatching, or the discontinuity flag Dis C(x, y, t) or the numericalvalue information determined by the threshold value of the displacementamount.

In Step S7, the three-dimensional spatial distribution informationanalysis unit 7 of the abnormality determination unit 6 determines thestatus of a crack, a separation, or an internal cavity, from thedisplacement amount or the displacement distribution diagram inY-direction having been input.

First, the determination method by way of pattern matching is described.The two-dimensional spatial distribution information analysis unit 7includes, as a database, a displacement distribution pattern created inadvance corresponding to a width, a depth, or the like of a crack, aninternal cavity, or a separation as illustrated in FIG. 14B, FIG. 16B,and FIG. 18B. The three-dimensional spatial distribution informationanalysis unit 7 performs pattern matching, by rotating or scaling up ordown these displacement distribution patterns with respect to thedisplacement distribution diagram in Y-direction input by thedisplacement separation unit 4, thereby determining the location or typeof the defect on the X-Y plane.

Next, the determining method by way of a threshold value of adisplacement amount is described. When there is a defect such as acrack, a separation, or an internal cavity, a displacement amount inY-direction is also generated. Therefore, when detecting a displacementamount which is greater than a pre-set threshold value, thethree-dimensional spatial distribution information analysis unit 7determines that there is a defect in that part, and sets an orthogonalflag ortho(x, y, t) to 1, and records, as numerical value information,the displacement amount data for the portion for which a displacementamount which is greater than the pre-set threshold value has beendetected.

The abnormality determination unit 6 inputs, to the abnormality mapcreation unit 9, the information on the defect determined by patternmatching, or the orthogonal flag ortho(x, y, t) or the numerical valueinformation determined by the displacement amount.

In Step S8, the three-dimensional spatial distribution informationanalysis unit 7 of the abnormality determination unit 6 determines astate of deterioration or a defect of a structure, from a moving amountin Z-direction having been input. The abnormality determination unit 6inputs the information on the deterioration or the defect having beendetermined, to the abnormality map creation unit 9.

In Step S9, the three-dimensional spatial distribution informationanalysis unit 7 of the abnormality determination unit 6 determines thestatus of a crack, a separation, or an internal cavity, from thedifferential displacement amount (stress value) or the differentialdisplacement distribution diagram (stress field) having been input.

First, the determination method by way of pattern matching is described.The three-dimensional spatial distribution information analysis unit 7includes, as a database, a displacement distribution pattern created inadvance corresponding to a width, a depth, or the like of a crack, aninternal cavity, or a separation as illustrated in FIG. 14C, FIG. 16C,and FIG. 18C. The three-dimensional spatial distribution informationanalysis unit 7 performs pattern matching, by rotating or scaling up ordown these displacement distribution patterns with respect to thedifferential displacement distribution diagram input by the differentialdisplacement calculation unit 5, thereby determining the location ortype of the defect on the X-Y plane.

Next, the determining method by way of a threshold value of adifferential displacement amount is described. In cracked portions, thestrain in X-direction, for example, increases sharply because itsdisplacement differential value diverges. For this reason, by providingin advance a threshold value for strain value, it is possible todetermine that there is a crack in a portion in which a strain exceedingthe threshold value is detected. The three-dimensional spatialdistribution information analysis unit 7 determines that there is acrack in the portion based on the input differential displacementamount, and sets the differential value flag Diff(x, y, t) to 1, andrecords, as numerical value information, the differential displacementamount data for the defective portion.

The abnormality determination unit 6 inputs, to the abnormality mapcreation unit 9, information on the defect determined by the patternmatching, or the differential value flag Diff(x, y, t) or the numericalvalue information determined by the differential displacement amount.

In Step S10, the displacement calculation unit 2 determines whether theprocessing of each frame image of the time-series images is completed.That is, if there are n frames in the time-series images, thedisplacement calculation unit 2 determines whether the processing ofn-th frame is completed. If the processing of the n frame images has notbeen completed (NO), the processing is repeated from Step S1. This isrepeated until the n frame images are processed. Note that “n” is notlimited to the total number of frames, and may be set to any number.When the processing of the n frame images has been completed (YES), theprocessing proceeds to Step S11.

In Step S11, the temporal change information analysis unit 8 of theabnormality determination unit 6 analyzes the time response of thedisplacement as illustrated in FIG. 17B or FIG. 19, based on thetime-series displacement amount or the displacement distribution diagramcorresponding to the n frame images. That is, from n displacementdistribution diagrams I(x, y, n), a time frequency distribution (timefrequency is denoted as “f”) is calculated as an amplitude A(x, y, z,f), and a phase P(x, y, z, f). When the time frequency distribution hasdifferent characteristic phases depending on the locations asillustrated in FIG. 17B, the temporal change information analysis unit 8determines that there is an internal cavity in a portion that undergoesphase shift. In addition, when the polarity of the displacement isreversed as illustrated in FIG. 19, the temporal change informationanalysis unit 8 determines that there is a separation in a portionbetween them. By comparing a period of a change of a moving amount inZ-direction or a period of a change of a differential value of a movingamount with a threshold value for a period provided in advance, thetemporal change information analysis unit 8 determines that thestructure is aged. The temporal change information analysis unit 8inputs the above-described time frequency distribution calculationresult and the defect determination result to the abnormality mapcreation unit 9.

In Step 12, the abnormality map creation unit 9 creates an abnormalitymap (x, y, z) based on the information input in the above-describedsteps. The result sent from the three-dimensional spatial distributioninformation analysis unit 7 and the temporal change information analysisunit 8 is a group of data related to the point (x, y, z) on the X-Y-Zcoordinates. For these pieces of data, the structure status isdetermined by the three-dimensional spatial distribution informationanalysis unit 7 and the temporal change information analysis unit 8 inthe abnormality determination unit 6.

These determinations are performed on the displacement amount or thedisplacement distribution diagram in X-direction, the displacementamount or the displacement distribution diagram in Y-direction, themoving amount in Z-direction, the differential displacement amount orthe differential displacement distribution diagram, or the time responsefor the displacement or the differential displacement. Therefore, evenwhen there is any lack of data, for example because of being unable tomake a determination in the displacement amount in Y-direction, theabnormality map creation unit 9 can still decide the status of thecorresponding portion in the X-Y coordinates, because determination hasbeen made for the displacement amount in X-direction and thedifferential displacement amount, and can create an abnormality map (x,y, z) based on this decision.

In the defect status determination, when there is any discrepancy indetermination among X-direction displacement, Y-direction displacement,Z-direction displacement, and differential displacement, the decisionmay be made by majority decision, or it is also possible to decide onthe item having the greatest difference from the threshold value beingthe determination reference.

In addition, the abnormality map creation unit 9 may represent thedegree of the defect based on various types of numerical valueinformation described above. For example, it is possible to representthe width or depth of the crack, the size of the separation, or the sizeor depth from a surface of the internal cavity.

It is also possible to perform determination of the defect status of thestructure, which is performed by the three-dimensional spatialdistribution information analysis unit 7 and the temporal changeinformation analysis unit 8 in the abnormality determination unit 6,while the abnormality map creation unit 9 creates the abnormality map(x, y, z). That is, analysis data may be obtained from thethree-dimensional spatial distribution information analysis unit 7 andthe temporal change information analysis unit 8, and the determinationof the defect status based on that analysis data may be performed by theabnormality map creation unit 9.

In addition, the output of the result from the abnormality map creationunit 9 may be information in the form in which a person can directlyview on a display device, or information in the form in which a machinecan read.

In the present example embodiment, the lens focal distance of theimage-capturing unit 11 may be 50 mm, and the pixel pitch may be 5 μm,so as to be able to obtain a pixel resolution of 500 μm at animage-capturing distance of 5 m. The image-capturing element of theimage-capturing unit 11 may be monochroic, and has 2000 pixelshorizontally and 2000 pixels vertically, to enable image-capturing therange of 1 m×1 m at an image-capturing distance of 5 m. The frame rateof the image-capturing element may be 60 Hz.

In addition, the sub-pixel displacement estimation by means of quadraticcurve interpolation is adopted in the image correlation in thedisplacement calculation unit 2, so as to realize displacementestimation up to 1/100 pixels, and to obtain the displacement resolutionof 5 μm displacement. The sub-pixel displacement estimation in imageestimation may adopt the various methods as described below. Inaddition, in displacement differential, a smoothing filter may be usedto reduce the noise when performing the differential operation.

Interpolation using quadratic curve, conformal straight line, or thelike may be used for the sub-pixel displacement estimation. In addition,for the image correlation operation, various methods such as SAD (Sum ofAbsolute Difference) method, or SSD (Sum of Squared Difference) method,NCC (Normalized Cross Correlation) method, and ZNCC (Zero-meanNormalized Cross Correlation) method may be used. It is also possible touse any combination between these methods and the above-describedsub-pixel displacement estimation method.

The lens focal distance of the image-capturing unit 11, and the pixelpitch, the pixel number, and the frame rate of the image-capturingelement may be changed, depending on the object to be measured, wherenecessary.

In the present example embodiment, the beam-like structure maycorrespond to a bridge, and the loading may correspond to a travelingvehicle. In the above description, loading was explained to be appliedon the beam-like structure. However, even when the loading moves on thebridge just as the traveling vehicle, a crack, an internal cavity, aseparation, and deterioration can be equally detected. In addition, thepresent example embodiment can be applied to any structure having adifferent material, size, or form, and to any loading method differentfrom the method to apply loading on the structure, for example a loadingmethod such as hanging the loading, as long as the structure can behavejust as in the above description from the viewpoint of materialmechanics.

In addition, not limited to time-series images, an array laser Dopplersensor, an array strain gauge, an array oscillation sensor, and an arrayacceleration sensor or the like may be used, as long it can measure thetime-series signals of a spatial two-dimensional distribution of thesurface displacement of a structure. The spatial two-dimensionaltime-series signals obtained from these array sensors may be treated asimage information.

In the present example embodiment, it is possible to obtain distanceinformation or tilt information for calculating the out-of-planedisplacement due to movement of a structure surface in the normaldirection, from the images obtained by image-capturing the structuresurface before and after loading application. In principle, it ispossible to obtain the moving amount of a structure surface in thenormal direction, by measuring the amount of deflection attributed tothe loading, from the direction of the side of the structure. However,when for example the structure is a bridge or the like, from anoperational point of view, it is extremely difficult to measure thebridge from its side, and therefore the measurement accuracy thereof isdegraded. The present example embodiment can resolve this operationaldifficulty, and therefore can amend the displacement of the images ofthe structure surface with high accuracy. In addition, in the presentexample embodiment, it is not necessary to provide such devices orfacilities to measure the amount of deflection from the direction of theside, which helps restrain the cost increase.

As described so far, according to the present example embodiments, it ispossible to detect with favorable accuracy any defect of a structure,such as cracks, separations, or internal cavities, remotely withoutcontact, while restraining costs.

The present invention is not limited to the above-described exampleembodiments, and can be modified in various ways within the scope of theinvention described in the claims, and these modifications are alsoincluded in the scope of the present invention.

Furthermore, a part of all of the above-described example embodimentscan also be described as, but not limited to, the followingsupplementary notes.

(Supplementary Note 1)

A status determination device comprising:

a displacement calculation unit that, from time-series images of astructure surface before and after loading application, calculates atwo-dimensional spatial distribution of a displacement of thetime-series images;

a depth moving amount calculation unit that calculates a moving amountof the structure surface in a normal direction due to the loadingapplication, from the two-dimensional spatial distribution of thedisplacement of the time-series images;

a displacement separation unit that calculates a correction amount basedon the moving amount, and separates a two-dimensional spatialdistribution of a displacement of the structure surface, by subtractingthe correction amount from the two-dimensional spatial distribution ofthe displacement of the time-series images; and

an abnormality determination unit that identifies a defect of thestructure, based on comparison of the two-dimensional spatialdistribution of the displacement of the structure surface and the movingamount, with a spatial distribution of a displacement having beenprepared in advance and a threshold value for the moving amount.

(Supplementary Note 2)

The status determination device according to Supplementary note 1,wherein

the depth moving amount calculation unit estimates a tilt angle of thestructure from the time-series images, and calculates the moving amountcorrected using the tilt angle.

(Supplementary Note 3)

The status determination device according to Supplementary note 1 or 2,comprising:

a differential displacement calculation unit that calculates atwo-dimensional differential spatial distribution from thetwo-dimensional spatial distribution of the displacement of thestructure surface, wherein

the abnormality determination unit identifies a defect of the structure,based on comparison between the two-dimensional differential spatialdistribution and a differential spatial distribution of a differentialdisplacement having been prepared in advance.

(Supplementary Note 4)

The status determination device according to any one of Supplementarynotes 1 to 3, wherein

the abnormality determination unit identifies a defect of the structure,based on a temporal change of the two-dimensional spatial distributionof the displacement of the structure surface.

(Supplementary Note 5)

The status determination device according to Supplementary note 3 or 4,wherein

the abnormality determination unit identifies a defect of the structure,based on a temporal change of the two-dimensional differential spatialdistribution.

(Supplementary Note 6)

The status determination device according to any one of Supplementarynotes 1 to 5, wherein

the abnormality determination unit identifies a defect of the structure,based on comparison between a displacement amount of the displacement ofthe structure surface and a threshold value having been prepared inadvance.

(Supplementary Note 7)

The status determination device according to any one of Supplementarynotes 3 to 6, wherein

the abnormality determination unit identifies a defect of the structure,based on comparison between a differential displacement amount of thedisplacement of the structure surface and a threshold value having beenprepared in advance.

(Supplementary Note 8)

The status determination device according to any one of Supplementarynotes 1 to 7, comprising:

an abnormality map creation unit that creates an abnormality map thatrepresents a location and a type of the defect, based on a determinationresult of the abnormality determination unit.

(Supplementary Note 9)

The status determination device according to any one of Supplementarynotes 1 to 8, wherein

the type of the defect includes a crack, a separation, and an internalcavity.

(Supplementary Note 10)

The status determination device according to Supplementary note 9,wherein

the prepared spatial distribution of the displacement and the prepareddifferential spatial distribution of the differential displacement arebased on information of the crack, the separation, and the internalcavity.

(Supplementary Note 11)

The status determination device according to any one of Supplementarynotes 1 to 10, wherein

the two-dimensional spatial distribution includes a distribution of anX-direction displacement of the displacement on an X-Y plane and adistribution of a Y-direction displacement of the displacement on theX-Y plane.

(Supplementary Note 12)

A status determination system comprising:

a status determination device that includes: a displacement calculationunit that, from time-series images of a structure surface before andafter loading application, calculates a two-dimensional spatialdistribution of a displacement of the time-series images; a depth movingamount calculation unit that calculates a moving amount of the structuresurface in a normal direction due to the loading application, from thetwo-dimensional spatial distribution of the displacement of thetime-series images; a displacement separation unit that calculates acorrection amount based on the moving amount, and separates atwo-dimensional spatial distribution of a displacement of the structuresurface, by subtracting the correction amount from the two-dimensionalspatial distribution of the displacement of the time-series images; andan abnormality determination unit that identifies a defect of thestructure, based on comparison of the two-dimensional spatialdistribution of the displacement of the structure surface and the movingamount, with a spatial distribution of a displacement having beenprepared in advance and a threshold value for the moving amount; and

an image-capturing unit that captures the time-series images andprovides the status determination device with the time-series images.

(Supplementary Note 13)

The status determination system according to Supplementary note 12,wherein

the depth moving amount calculation unit estimates a tilt angle of thestructure from the time-series images, and calculates the moving amountcorrected using the tilt angle.

(Supplementary Note 14)

The status determination system according to Supplementary note 12 or13, comprising:

a differential displacement calculation unit that calculates atwo-dimensional differential spatial distribution from thetwo-dimensional spatial distribution of the displacement of thestructure surface, wherein

the abnormality determination unit identifies a defect of the structure,based on comparison between the two-dimensional differential spatialdistribution and a differential spatial distribution of a differentialdisplacement having been prepared in advance.

(Supplementary Note 15)

The status determination system according to any one of Supplementarynotes 12 to 14, wherein

the abnormality determination unit identifies a defect of the structure,based on a temporal change of the two-dimensional spatial distributionof the displacement of the structure surface.

(Supplementary Note 16)

The status determination system according to Supplementary note 14 or15, wherein

the abnormality determination unit identifies a defect of the structure,based on a temporal change of the two-dimensional differential spatialdistribution.

(Supplementary Note 17)

The status determination system according to any one of Supplementarynote 12 to 16, wherein

the abnormality determination unit identifies a defect of the structure,based on comparison between a displacement amount of the displacement ofthe structure surface and a threshold value having been prepared inadvance.

(Supplementary Note 18)

The status determination system according to any one of Supplementarynotes 14 to 17, wherein

the abnormality determination unit identifies a defect of the structure,based on comparison between a differential displacement amount of thedisplacement of the structure surface and a threshold value having beenprepared in advance.

(Supplementary Note 19)

The status determination system according to any one of Supplementarynote 12 to 18, comprising:

an abnormality map creation unit that creates an abnormality map thatrepresents a location and a type of the defect, based on a determinationresult of the abnormality determination unit.

(Supplementary Note 20)

The status determination system according to any one of Supplementarynotes 12 to 19, wherein the type of the defect includes a crack, aseparation, and an internal cavity.

(Supplementary Note 21)

The status determination system according to Supplementary note 20,wherein

the prepared spatial distribution of the displacement and the prepareddifferential spatial distribution of the differential displacement arebased on information of the crack, the separation, and the internalcavity.

(Supplementary Note 22)

The status determination system according to any one of Supplementarynotes 12 to 21, wherein

the two-dimensional spatial distribution includes a distribution of anX-direction displacement of the displacement on an X-Y plane and adistribution of a Y-direction displacement of the displacement on theX-Y plane.

(Supplementary Note 23)

A status determination method comprising:

calculating, from time-series images of a structure surface before andafter loading application, a two-dimensional spatial distribution of adisplacement of the time-series images;

calculating a moving amount of the structure surface in a normaldirection due to the loading application, from the two-dimensionalspatial distribution of the displacement of the time-series images;

calculating a correction amount based on the moving amount;

separating a two-dimensional spatial distribution of a displacement ofthe structure surface, by subtracting the correction amount from thetwo-dimensional spatial distribution of the displacement of thetime-series images; and

identifying a defect of the structure, based on comparison of thetwo-dimensional spatial distribution of the displacement of thestructure surface and the moving amount, with a spatial distribution ofa displacement having been prepared in advance and a threshold value forthe moving amount.

(Supplementary Note 24)

The status determination method according to Supplementary note 23,wherein

a tilt angle of the structure is estimated from the time-series images,and the moving amount having been corrected using the tilt angle iscalculated.

(Supplementary Note 25)

The status determination method according to Supplementary note 23 or24, comprising:

calculating a two-dimensional differential spatial distribution of thetwo-dimensional spatial distribution, from the two-dimensional spatialdistribution, wherein

a defect of the structure is identified, based on comparison between thetwo-dimensional differential spatial distribution and a differentialspatial distribution of a differential displacement having been preparedin advance.

(Supplementary Note 26)

The status determination method according to any one of Supplementarynotes 23 to 25, wherein

a defect of the structure is identified, based on a temporal change ofthe two-dimensional spatial distribution of the displacement of thestructure surface.

(Supplementary Note 27)

The status determination method according to Supplementary note 25 or26, wherein

a defect of the structure is identified, based on a temporal change ofthe two-dimensional differential spatial distribution.

(Supplementary Note 28)

The status determination method according to any one of Supplementarynotes 23 to 27, wherein

a defect of the structure is identified, based on comparison between adisplacement amount of the displacement of the structure surface and athreshold value having been prepared in advance.

(Supplementary Note 29)

The status determination method according to any one of Supplementarynotes 25 to 28, wherein

a defect of the structure is identified, based on comparison between adifferential displacement amount of the displacement of the structuresurface and a threshold value having been prepared in advance.

(Supplementary Note 30)

The status determination method according to any one of Supplementarynotes 23 to 29, comprising:

creating an abnormality map that represents a location and a type of thedefect, based on the identification result.

(Supplementary Note 31)

The status determination method according to any one of Supplementarynotes 23 to 30, wherein

the type of the defect includes a crack, a separation, and an internalcavity.

(Supplementary Note 32)

The status determination method according to Supplementary note 31,wherein

the prepared spatial distribution of the displacement and the prepareddifferential spatial distribution of the differential displacement arebased on information of the crack, the separation, and the internalcavity.

(Supplementary Note 33)

The status determination method according to any one of Supplementarynotes 23 to 32, wherein

the two-dimensional spatial distribution includes a distribution of anX-direction displacement of the displacement on an X-Y plane and adistribution of a Y-direction displacement of the displacement on theX-Y plane.

(Supplementary Note 34)

A status determination device comprising:

a depth moving amount calculation unit that calculates a moving amountof a structure surface in a normal direction due to loading application;and

an abnormality determination unit that identifies a defect of thestructure, based on comparison between the moving amount and a thresholdvalue for the moving amount having been prepared in advance.

(Supplementary Note 35)

The status determination device according to Supplementary note 34,comprising:

a displacement calculation unit that, from time-series images of thestructure surface before and after loading application, calculates atwo-dimensional spatial distribution of a displacement of thetime-series images; and

the depth moving amount calculation unit calculates the moving amountfrom the two-dimensional spatial distribution of the displacement of thetime-series images.

(Supplementary Note 36)

The status determination device according to Supplementary note 35,wherein

the depth moving amount calculation unit estimates a tilt angle of thestructure from the time-series images, and calculates the moving amountcorrected using the tilt angle.

(Supplementary Note 37)

The status determination device according to any one of Supplementarynotes 34 to 36, comprising:

a differential displacement calculation unit that calculates adifferential displacement amount of the moving amount, wherein

the abnormality determination unit identifies a defect of the structure,based on comparison between the differential displacement amount of themoving amount and a differential displacement amount having beenprepared in advance.

(Supplementary Note 38)

The status determination device according to any one of Supplementarynotes 35 to 37, comprising:

a displacement separation unit that calculates a correction amount basedon the moving amount, and separates a two-dimensional spatialdistribution of a displacement of the structure surface, by subtractingthe correction amount from the two-dimensional spatial distribution ofthe displacement of the time-series images, wherein

the abnormality determination unit identifies a defect of the structure,based on comparison between the two-dimensional spatial distribution ofthe displacement of the structure surface and a spatial distribution ofa displacement having been prepared in advance.

(Supplementary Note 39)

The status determination device according to Supplementary note 37 or38, wherein

the differential displacement calculation unit calculates atwo-dimensional differential spatial distribution from thetwo-dimensional spatial distribution of the displacement of thestructure surface, and

the abnormality determination unit identifies a defect of the structure,based on comparison between the two-dimensional differential spatialdistribution and a differential spatial distribution of a differentialdisplacement having been prepared in advance.

(Supplementary Note 40)

The status determination device according to any one of Supplementarynotes 34 to 39, wherein

the abnormality determination unit identifies a defect of the structure,based on a temporal change of the moving amount or the two-dimensionalspatial distribution of the displacement of the structure surface.

(Supplementary Note 41)

The status determination device according to any one of Supplementarynotes 37 to 40, wherein

the abnormality determination unit identifies a defect of the structure,based on a temporal change of the differential displacement amount ofthe moving amount or the two-dimensional differential spatialdistribution.

(Supplementary Note 42)

The status determination device according to any one of Supplementarynotes 34 to 41, comprising:

an abnormality map creation unit that creates an abnormality map thatrepresents a location and a type of the defect, based on a determinationresult of the abnormality determination unit.

(Supplementary Note 43)

A status determination method comprising:

calculating a moving amount of a structure surface in a normal directiondue to loading application; and

identifying a defect of the structure, based on comparison between themoving amount and a threshold value for the moving amount having beenprepared in advance.

(Supplementary Note 44)

The status determination method according to Supplementary note 43,comprising:

calculating, from time-series images of the structure surface before andafter loading application, a two-dimensional spatial distribution of adisplacement of the time-series images, wherein

the moving amount is calculated from the two-dimensional spatialdistribution of the displacement of the time-series images.

(Supplementary Note 45)

The status determination method according to Supplementary note 44,wherein

a tilt angle of the structure is estimated from the time-series images,and the moving amount corrected using the tilt angle is calculated.

(Supplementary Note 46)

The status determination method according to any one of Supplementarynotes 43 to 45, comprising:

calculating a differential displacement amount of the moving amount,wherein

a defect of the structure is identified, based on comparison between thedifferential displacement amount of the moving amount and a differentialdisplacement amount having been prepared in advance.

(Supplementary Note 47)

The status determination method according to any one of Supplementarynotes 44 to 46, comprising:

calculating a correction amount based on the moving amount, andseparating a two-dimensional spatial distribution of a displacement ofthe structure surface, by subtracting the correction amount from thetwo-dimensional spatial distribution of the displacement of thetime-series images, wherein

a defect of the structure is identified, based on comparison between thetwo-dimensional spatial distribution of the displacement of thestructure surface and a spatial distribution of a displacement havingbeen prepared in advance.

(Supplementary Note 48)

The status determination method according to Supplementary note 47,wherein

a two-dimensional differential spatial distribution is calculated fromthe two-dimensional spatial distribution of the displacement of thestructure surface, and

a defect of the structure is identified, based on comparison between thetwo-dimensional differential spatial distribution and a differentialspatial distribution of a differential displacement having been preparedin advance.

(Supplementary Note 49)

The status determination method according to any one of Supplementarynotes 43 to 48, wherein

a defect of the structure is identified, based on a temporal change ofthe moving amount or the two-dimensional spatial distribution of thedisplacement of the structure surface.

(Supplementary Note 50)

The status determination method according to any one of Supplementarynotes 46 to 49, wherein

a defect of the structure is identified, based on a temporal change ofthe differential displacement amount of the moving amount or thetwo-dimensional differential spatial distribution.

(Supplementary Note 51)

The status determination method according to any one of Supplementarynotes 43 to 50, comprising:

creating an abnormality map that represents a location and a type of thedefect.

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2015-057048, filed on Mar. 20, 2015, thedisclosure of which is incorporated herein in its entirety by reference.

INDUSTRIAL APPLICABILITY

The present invention can be applied to devices and systems that detectsuch defects as a crack, a separation, and an internal cavity generatedin a structure such as a tunnel and a bridge, by observing from a remotelocation.

REFERENCE SIGNS LIST

-   1, 100 status determination device-   2 displacement calculation unit-   3 depth moving amount calculation unit-   4 displacement separation unit-   5 differential displacement calculation unit-   6 abnormality determination unit-   7 three-dimensional spatial distribution information analysis unit-   8 temporal change information analysis unit-   9 abnormality map creation unit-   10 status determination system-   11 image-capturing unit-   12 structure-   13 defect

What is claimed is:
 1. A status determination device comprising: adisplacement calculation circuit that, from time-series images of astructure surface before and after loading application, calculates atwo-dimensional spatial distribution of a displacement of thetime-series images; a depth moving amount calculation circuit thatcalculates a moving amount of the structure surface in a normaldirection due to the loading application, from the two-dimensionalspatial distribution of the displacement of the time-series images; adisplacement separation circuit that calculates a correction amountbased on the moving amount, and separates a two-dimensional spatialdistribution of a displacement of the structure surface, by subtractingthe correction amount from the two-dimensional spatial distribution ofthe displacement of the time-series images; and an abnormalitydetermination circuit that identifies a defect of the structure, basedon comparison of the two-dimensional spatial distribution of thedisplacement of the structure surface and the moving amount, with aspatial distribution of a displacement having been prepared in advanceand a threshold value for the moving amount.
 2. The status determinationdevice according to claim 1, wherein the depth moving amount calculationcircuit estimates a tilt angle of the structure from the time-seriesimages, and calculates the moving amount corrected using the tilt angle.3. The status determination device according to claim 1, comprising: adifferential displacement calculation circuit that calculates atwo-dimensional differential spatial distribution from thetwo-dimensional spatial distribution of the displacement of thestructure surface, wherein the abnormality determination circuitidentifies a defect of the structure, based on comparison between thetwo-dimensional differential spatial distribution and a differentialspatial distribution of a differential displacement having been preparedin advance.
 4. The status determination device according to claim 1,wherein the abnormality determination circuit identifies a defect of thestructure, based on a temporal change of the two-dimensional spatialdistribution of the displacement of the structure surface.
 5. The statusdetermination device according to claim 3, wherein the abnormalitydetermination circuit identifies a defect of the structure, based on atemporal change of the two-dimensional differential spatialdistribution.
 6. The status determination device according to claim 1,comprising: an abnormality map creation circuit that creates anabnormality map that represents a location and a type of the defect,based on a determination result of the abnormality determinationcircuit.
 7. A status determination system comprising: a statusdetermination device according to claim 1; and an image-capture devicethat captures the time-series images and provides the statusdetermination device with the time-series images.
 8. A statusdetermination method comprising: calculating, from time-series images ofa structure surface before and after loading application, atwo-dimensional spatial distribution of a displacement of thetime-series images; calculating a moving amount of the structure surfacein a normal direction due to the loading application, from thetwo-dimensional spatial distribution of the displacement of thetime-series images; calculating a correction amount based on the movingamount; separating a two-dimensional spatial distribution of adisplacement of the structure surface, by subtracting the correctionamount from the two-dimensional spatial distribution of the displacementof the time-series images; and identifying a defect of the structure,based on comparison of the two-dimensional spatial distribution of thedisplacement of the structure surface and the moving amount, with aspatial distribution of a displacement having been prepared in advanceand a threshold value for the moving amount.
 9. A status determinationdevice comprising: a displacement calculation circuit that, fromtime-series images of a structure surface before and after loadingapplication, calculates a two-dimensional spatial distribution of adisplacement of the time-series images; a depth moving amountcalculation circuit that calculates a moving amount of the structuresurface in a normal direction due to the loading application, from thetwo-dimensional spatial distribution of the displacement of thetime-series images; a displacement separation circuit that calculates acorrection amount based on the moving amount, and separates atwo-dimensional spatial distribution of a displacement of the structuresurface, by subtracting the correction amount from the two-dimensionalspatial distribution of the displacement of the time-series images; andan abnormality determination circuit that identifies a defect of thestructure, based on comparison between the moving amount and a thresholdvalue for the moving amount having been prepared in advance.